Patent GB-922419-A (GB)
Title: Improvements in pneumatic servo-control clutch actuating apparatus
IPC: F16D48/02
Filed: 1960-02-15
Abstract: 922,419. Fluid-pressure servomotor control systems. FABBRICA ITALIANIA MAGNETI MARELLI S.p.A. Feb. 15, 1960 [March 26, 1959], No. 5357/60. Class 135. [Also in Group XXIV] A self-contained clutch actuating follow-up servomotor and change-speed control for a motor car comprises a rod 2 moved downwards of the Figure by the car driver to act through a universally mounted lever 11 engaging at one side with a stop 13 on a piston 5 and at the other upon a pipe 10 which slides relatively to the piston and opens a valve 9, so that compressed air supplied through a port A and a chamber 30 to a central bore 16 in the rod 2 and to a chamber 15 is admitted to the space 32 behind the piston which slides within the servomotor casing 1, the resulting downward movement of the piston 5 drawing a rod 4 downwards to act through links (not further described) and disengage the main clutch, completion of the downwards movement of the piston bringing a plate 20 fast therewith into engagement with a pipe 19 slidably supported in a casing wall 17 to open a valve 18, by which compressed air in the chamber 30 is admitted through a port 21 and a pressure-reducing valve 22 to a port B leading to ratio establishing servo means in the change-speed gear, the plate 20 also engaging a cam rod 25 slidden downwards against the bias of a spring 26 to actuate a switch I in a circuit controlling electromagnetic valves in the ratio establishing means. On release of the clutch pedal by the driver, clutch release springs slide the rod 2 upwards, and the pipe 19 is restored to the position shown relatively to the casing wall 17 to allow venting of compressed air from the ratio establishing servo means through the pipe B, the valve 22, the space 21 and through the pipe 19 to a central space 37 in the servo housing 1 and thence through an exhaust outlet 38 to the atmosphere. Simultaneously, the upward movement of the rod 2 and the universally mounted lever 11 allows the pipe 10 to return to the position shown relatively to the piston 5, whereby the space 32 behind the piston is vented through this pipe to a space 7 in turn connected to the space 37 and the exhaust outlet 38. The usual clutch springs can now draw the rod 4, the piston 5 &c. upwards and restore the position shown, the initial clutch re-engaging movement allowing the spring 26 to slide the cam rod 25 so that the switch I is again restored to its initial condition. The pressure control valve 22 comprises a piston 23 biased to the valve open position by a calibrated spring 24 in opposition to the bias of a spring 34, increasing pressure in the pipes leading from the port B to the ratio establishing servos acting against the bias of the spring 24 to close the valve when a predetermined pressure has been achieved. Should the source of compressed air fail, direct mechanical actuation of the clutch rod 4 is obtained by depression of the clutch pedal to draw the rod 2 downwards, the universally mounted lever 11 engaging a second stop 14 in the piston 5, as well as the stop 13, when the valve 9 has been opened, so that the piston &c. is drawn downwards by mechanical contact between the parts.